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J Biol Chem. 2002 Jul 26;277(30):27217-26. Epub 2002 May 8.

Ionomycin-activated calpain triggers apoptosis. A probable role for Bcl-2 family members.

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1
Abteilung für Klinische Chemie und Klinische Biochemie, Chirurgische Klinik Innenstadt, Klinikum der LMU München, Nussbaumstrasse 20, D-80336 Münich, Germany. shirgilpa@web.de

Abstract

Ubiquitous calpains (mu- and m-calpain) have been repeatedly implicated in apoptosis, but the underlying mechanism(s) remain(s) to be elucidated. We examined ionomycin-induced cell death in LCLC 103H cells, derived from a human large cell lung carcinoma. We detected hallmarks of apoptosis such as membrane blebbing, nuclear condensation, DNA ladder formation, caspase activation, and poly-(ADP-ribose)polymerase cleavage. Apoptosis was prevented by preincubation of the cells with the calpain inhibitor acetyl-calpastatin 27-peptide and the caspase inhibitor Z-DEVD-fmk, implicating both the calpains and caspases in the apoptotic process. The apoptotic events correlated in a calpastatin-inhibitable manner with Bid and Bcl-2 decrease and with activation of caspases-9, -3, and -7. In vitro both ubiquitous calpains cleaved recombinant Bcl-2, Bid, and Bcl-x(L) at single sites truncating their N-terminal regions. Binding studies revealed diminished interactions of calpain-truncated Bcl-2 and Bid with immobilized intact Bcl-2 family proteins. Moreover, calpain-cleaved Bcl-2 and Bid induced cytochrome c release from isolated mitochondria. We conclude that ionomycin-induced calpain activation promotes decrease of Bcl-2 proteins thereby triggering the intrinsic apoptotic pathway.

PMID:
12000759
DOI:
10.1074/jbc.M202945200
[Indexed for MEDLINE]
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